T3W4 SCGS 2023 4OLP Bio Prelim P2 MS

1 SINGAPORE CHINESE GIRLS’ SCHOOL PRELIMINARY EXAMINATION CANDIDATE NAME ANSWERS CLASS REGISTER NUMBER CENTRE NUMBER INDEX NUMBER BIOLOGY 6093/02 Paper 2 Wednesday 23 August 2023 1 hour 45 minutes No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your class, index number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. Section A Answer all questions. Section B Answer all questions. The last question has a choice of parts to answer. The use of an approved scientific calculator is expected, where appropriate. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. T his question paper consists of 18 printed pages and 1 blank page. For Examiner’s Use Section A 50 Qn 7 10 Qn 8 10 9 10 Total 80

2 Section A Answer all questions. Write your answer in the spaces provided. 1 Fig. 1.1 sho ws how a blocked blood vessel outside the heart can be by passed using an artificial blood vessel. Fig. 1.1 (a) Name the blocked blood vessel and vessel A respectively. ............................................................................................................................. [2] (b) Describe how the blocked blood vessel in Fig 1.1 can affect the normal functioning of the heart. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................ . [2] vessel A artificial blood vessel fixed into vessel A blocked blood vessel -less oxygen and glucose delivered to heart muscles for aerobic respiration Heart muscle cells die leading to heart attack Blocked blood vessel: Coronary artery Vessel A: aorta

3 (c) Sometimes, instead of using an artificial blood vessel, a vein from another part in the patient’s body is used. Suggest two ways in which a vein might not be suitable for this purpose. 1 ................................................................................................................................ ................................................................................................................................... 2 ................................................................................................................................ ............................................................................................................................... [2] (d) Fig. 1.2 shows the same blocked blood vessel in Fig 1.1, with a ‘stent’ in place. Fig. 1.2 (i) Name a substance that can cause the blockage B. ....................................................................................................................... [1] (ii) Insertion of the ‘stent’ can cause damage to the surrounding tissues around the blockage B. Suggest and explain why patients are given ‘anti-platelet’ drugs before inserting the ‘stent’. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ....................................................................................................................... [2] B blood vessel with blockage B • Thinner muscular walls hence less able to withstand high pressure ; • Presence of valves, hence blood travel slower/ impede blood flow ; • Less elastic fibre / tissue hence less able to stretch and recoil; • Large lumen relative to diameter, hence speed of blood slows down (any 2) R:small walls, thin without mentioning about the walls ; treated as foreign body and rejected by immune system Fat deposits/cholesterol • natural response for blood to clot due to damage or injury caused by insertion of the stent; • anti-platelets drug administered to prevent platelets + release thrombokinase/cause fibrinogen to change to fibrin ; R: agglutination

4 e) The blood in blood vessel A contains 20 cm3 of oxygen per 100 cm3 of blood. 98.5% of the oxygen is carried in red blood cells. The remaining percentage is carried in solution in the blood plasma. Calculate the volume of oxygen carried in the blood plasms per 100 cm3 of blood. Show your working. ……………………………………[1] [Total: 10 marks] (1.5/100) x 20; = 0.3 cm3;

5 2 Fig. 2.1 shows a diagram of a developing mammalian foetus and part of the uterus wall. Fig. 2.1 (a) Identify C and D. .............................................................................................................................. [1] (b) State two functions of D. ................................................................................................................................... ................................................................................................................................... ............................................................................................................................... [2] (b) Suggest how smoking affects the supply of oxygen and nutrients to structure E during pregnancy. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ............................................................................................................................... [3] C D E spongy lining of uterus Amniotic fluid supports and cushions the fetus. Absorbs shocks and as it cannot be compressed, protects the fetus against physical injury (damage AWW). Amniotic fluid lubricates and reduces friction in the vagina or birth canal during birth Allows fetus space for movement during growth. (any two) Reject: maintain internal temperature / provide nutrients / protects fetus (how exactly/what from?) • Structure E is the placenta. Cigarette smoke contains nicotine which causes the release of adrenaline. This will cause the maternal arteries to become narrow and the blood supply to the placenta to decrease. Accept: Carbon monoxide/nicotine increases fatty deposits in walls of artery which narrows lumen • Cigarette smoke also contains carbon monoxide, which binds more readily to haemoglobin to form carboxyhaemoglobin, reducing the ability of haemoglobin to carry oxygen in the red blood cells. (m